Multilayer structures for daytime radiative cooling and electromagnetic interference shielding

We present multilayer thin films that simultaneously provide strong electromagnetic interference (EMI) shielding and passive daytime radiative cooling. Using a multi-objective optimization framework, we explored multilayer stacks composed of common dielectric and metallic materials. The optimization shows that shielding effectiveness (SE) exceeding 70 dB across the 1 to 40 GHz frequency range and cooling performance above 70 W/m2 can be achieved simultaneously under 1-sun illumination and the U.S. Standard Atmosphere in the ideal dry limit (precipitable water = 0 mm). The analysis of the optimized designs reveals a consistent combination of Si3N4 and SiO2 dielectric layers on a metallic substrate. In these systems, the dielectric layers enhance mid-infrared emission within the atmospheric window (8–13 µm), while the metal layer provides strong EMI attenuation and high solar reflectivity. Structures such as Si3N4/Ag and Si3N4/SiO2/Ag achieve daytime net cooling power densities of 48.4 and 73.4 W/m2, respectively, while maintaining shielding effectiveness above 90 dB for 1–40 GHz. Al can also serve as a more cost-effective metallic layer, although with reduced net cooling performance. The two-layer system of SiO2/Al achieves a modest positive net cooling power density of 5.4 W/m2, while the three-layer Si3N4/SiO2/Al system improves the net cooling power density to 55.0 W/m2. These results demonstrate a scalable strategy for designing multifunctional coatings that combine EMI shielding with passive radiative cooling.